A pocket penetrometer is a fantastic little invention which geotechnical engineers and technologists find very handy. It is a small handheld gauge which contains a telescoping rod which can be pushed into the soil. The distance the rod goes into the soil corresponds to a compressive strength on the dial.
Measurement of Soil
The pocket penetrometer measures the compressive strength of the soil. Most penetrometers available today contain units of tons/ft2 or kg/cm2, and the compressive strength is read directly from the gauge. Some common conversions are:
1 ton/ft2 = 2000 psf = 13.9 psi
1 kg/cm2 = 98.1 kPa
Limitations
A pocket penetrometer is a primative instrument that is subject to many errors such as non-uniform soil. As a minimum, you should take a series of measurements in one area and average them. The penetrometer should not replace laboratory testing or field analysis, or be used to produce foundation design data.
Dominique Gorana says
April 2, 2017 at 8:44 pmWhere can I find the best pocket penetrometer?
Jon Hartney says
May 15, 2017 at 9:59 amThere are a number of places you can find a penetrometer, even at a local hardware store. Here’s my recommendation from what I’ve found online:
9903912 Adapter Foot to Soil Penetrometer, Measures Low-Strength Cohesive Soils
Mike Stuart says
May 17, 2017 at 1:31 pmYou can’t go wrong with Humboldt (above) or Gilson (below):
HM-500 Gilson Pocket Penetrometer
Colin Basye says
June 8, 2017 at 11:04 amIs there an ASTM or AASHTO standard procedure for using the device?
geomineral.ru says
June 12, 2017 at 9:55 amThe determination of the unconsolidated, undrained strength of cohesive soils with lateral confinement is covered by Test Method